The Monetary policy rules and the inflation process in open emerging

This paper has three objectives. First, it aims at revealing the logic of interest rate setting pursued by monetary authorities of 12 new EU members. Using estimation of an augmented Taylor rule, we find that this setting was not always consistent with the official monetary policy. Second, we seek to shed light on the inflation process of these countries. To this end, we carry out an estimation of an open economy Philips curve (PC). Our main finding is that inflation rates were not only driven by backward persistency but also held a forward-looking component. Finally, we assess the viability of existing monetary arrangements for price stability. The analysis of the conditional inflation variance obtained from GARCH estimation of PC is used for this purpose. We conclude that inflation targeting is preferable to an exchange rate peg because it allowed decreasing the inflation rate and anchored its volatility.

Delay and Haircuts in Sovereign Debt: Recovery and Sustainability

One of the striking aspects of recent sovereign debt restructurings is, conditional on default, delay length is positively correlated with the size of "haircut", which is size of creditor losses. In this paper, we develop an incomplete information model of debt restructuring where the prospect of uncertain economic recovery and the signalling about sustainability concerns together generate multi-period delay. The results from our analysis show that there is a correlation between delay length and size of haircut. Such results are supported by evidence. We show that Pareto ranking of equilibria, conditional on default, can be altered once we take into account the ex ante incentive of sovereign debtor. We use our results to evaluate proposals advocated to ensure orderly resolution of sovereign debt crises.

Multiple Objectives in Monetary Policy: A de Facto Analysis for ‘Advanced’ Countries

A statistical methodology is developed by which realised outcomes can be used to identify, for calendar years between 1974 and 2012, when policy makers in ‘advanced’ economies have successfully pursued single objectives of different kinds, or multiple objectives. A simple criterion is then used to distinguish between multiple objectives pure and simple and multiple objectives subject to a price stability constraint. The overall and individual country results which this methodology produces seem broadly plausible. Unconditional and conditional analyses of the inflation and growth associated with different types of objectives reveal that multiple objectives subject to a price stability constraint are associated with roughly as good economic performance as the single objective of inflation. A proposal is then made as to how the remit of an inflation-targeting central bank could be adjusted to allow it to pursue other objectives in extremis without losing the credibility effects associated with inflation targeting.

Innovation sources and productivity in Catalonian firms: a quantile regression analysis

This paper explores the effects of two main sources of innovation - intramural and external R&D— on the productivity level in a sample of 3,267 Catalonian firms. The data set used is based on the official innovation survey of Catalonia which was a part of the Spanish sample of CIS4, covering the years 2002-2004. We compare empirical results by applying usual OLS and quantile regression techniques both in manufacturing and services industries. In quantile regression, results suggest different patterns at both innovation sources as we move across conditional quantiles. The elasticity of intramural R&D activities on productivity decreased when we move up the high productivity levels both in manufacturing and services sectors, while the effects of external R&D rise in high-technology industries but are more ambiguous in low-technology and knowledge-intensive services. JEL codes: O300, C100, O140 Keywords: Innovation sources, R&D, Productivity, Quantile Regression

Normal hemopoiesis and lymphopoiesis in the combined absence of numb and numblike.

The mammalian ortholog of the conserved Drosophila adaptor protein Numb (Nb) and its homolog Numblike (Nbl) modulate neuronal cell fate determination at least in part by antagonizing Notch signaling. Because the Notch pathway has been implicated in regulating hemopoietic stem cell self-renewal and T cell fate specification in mammals, we investigated the role of Nb and Nbl in hemopoiesis using conditional gene targeting. Surprisingly simultaneous deletion of both Nb and Nbl in murine bone marrow precursors did not affect the ability of stem cells to self-renew or to give rise to differentiated myeloid or lymphoid progeny, even under competitive conditions in mixed chimeras. Furthermore, T cell fate specification and intrathymic T cell development were unaffected in the combined absence of Nb and Nbl. Collectively our data indicate that the Nb family of adaptor proteins is dispensable for hemopoiesis and lymphopoiesis in mice, despite their proposed role in neuronal stem cell development.

Some Considerations Concerning Regulation and Competition in the Port Sector

The aim of this paper is to discuss the circumstances in which the process of competition between ports takes place in Spain − circumstances arising from the way the port system is currently set up and from the regulations governing it. The importance of this matter lies both in the fact that intensified competition between ports is the way to set about boosting the efficiency of the Spanish port sector and in the relevance of this business to the economies of the regions in which the ports are located. It is precisely for this reason that the reform instituted in 1992 aimed to combine balanced development of the national port system with the defence of the interests of autonomous regions. To this end the current regulatory framework provides for the possibility of port authorities drawing up their own competitive strategies, but makes their implementation conditional upon approval of their business plan by the Spanish state port authority. The latter body coordinates the national port system to ensure the guidelines set by the central government authorities are followed in the field of transport. However, the scale of the differences which exist among both the size of facilities and their relevant markets on the one hand, and the financial and economic circumstances of each of them on the other, suggest that each port authority's needs must be very different. Consequently, their competitive strategies must also be very different. It is therefore valid to ask whether coping with this diversity calls for different guidelines to regulate their freedom of action. Key words: Competition, regulation, port sector JEL classification numbers: L1, L5, L9

Neural Wiskott-Aldrich syndrome protein modulates Wnt signaling and is required for hair follicle cycling in mice.

The Rho family GTPases Cdc42 and Rac1 are critical regulators of the actin cytoskeleton and are essential for skin and hair function. Wiskott-Aldrich syndrome family proteins act downstream of these GTPases, controlling actin assembly and cytoskeletal reorganization, but their role in epithelial cells has not been characterized in vivo. Here, we used a conditional knockout approach to assess the role of neural Wiskott-Aldrich syndrome protein (N-WASP), the ubiquitously expressed Wiskott-Aldrich syndrome-like (WASL) protein, in mouse skin. We found that N-WASP deficiency in mouse skin led to severe alopecia, epidermal hyperproliferation, and ulceration, without obvious effects on epidermal differentiation and wound healing. Further analysis revealed that the observed alopecia was likely the result of a progressive and ultimately nearly complete block in hair follicle (HF) cycling by 5 months of age. N-WASP deficiency also led to abnormal proliferation of skin progenitor cells, resulting in their depletion over time. Furthermore, N-WASP deficiency in vitro and in vivo correlated with decreased GSK-3beta phosphorylation, decreased nuclear localization of beta-catenin in follicular keratinocytes, and decreased Wnt-dependent transcription. Our results indicate a critical role for N-WASP in skin function and HF cycling and identify a link between N-WASP and Wnt signaling. We therefore propose that N-WASP acts as a positive regulator of beta-catenin-dependent transcription, modulating differentiation of HF progenitor cells.

Generation and phenotypic analysis of protein S-deficient mice.

Protein S (PS) is an important natural anticoagulant with potentially multiple biologic functions. To investigate further the role of PS in vivo, we generated Pros(+/-) heterozygous mice. In the null (-) allele, the Pros exons 3 to 7 have been excised through conditional gene targeting. Pros(+/-) mice did not present any signs of spontaneous thrombosis and had reduced PS plasma levels and activated protein C cofactor activity in plasma coagulation and thrombin generation assays. Tissue factor pathway inhibitor cofactor activity of PS could not be demonstrated. Heterozygous Pros(+/-) mice exhibited a notable thrombotic phenotype in vivo when challenged in a tissue factor-induced thromboembolism model. No viable Pros(-/-) mice were obtained through mating of Pros(+/-) parents. Most E17.5 Pros(-/-) embryos were found dead with severe intracranial hemorrhages and most likely presented consumptive coagulopathy, as demonstrated by intravascular and interstitial fibrin deposition and an increased number of megakaryocytes in the liver, suggesting peripheral thrombocytopenia. A few E17.5 Pros(-/-) embryos had less severe phenotype, indicating that life-threatening manifestations might occur between E17.5 and the full term. Thus, similar to human phenotypes, mild heterozygous PS deficiency in mice was associated with a thrombotic phenotype, whereas total homozygous deficiency in PS was incompatible with life.

Attrition of Households and Individuals in Panel Surveys

Attrition is mostly caused by not contacted or refusing sample members. On one hand it is well-known that reasons to attrite due to non-contact are different from those that are due to refusal. On the other hand does non-contact most probably affect household attrition, while refusal can be effective on both households and individuals. In this article, attrition on both the household and (conditional on household participation) the individual level is analysed in three panel surveys from the Cross National Equivalent File (CNEF): the German Socio- Economic Panel (GSOEP), the British Household Panel Study (BHPS), and the Swiss Household Panel (SHP). To follow households over time we use a common rule in all three surveys. First, we find different attrition magnitudes and patterns both across the surveys and also on the household and the individual level. Second, there is more evidence for reinforced rather than compensated household level selection effects if the individual level is also taken into account.

The role of the Estrogen-Responsive B box protein in skin morphogenesis, wound repair and skin disease

SUMMARY: EBBP is a poorly characterized member of the RBCC/TRIM family (RING finger B-box coiled-coilltripartite motif). It is ubiquitously expressed, but particularly high levels are found in keratinocytes. There is evidence that EBBP is involved in inflammatory processes, since it can interact with pro-interleukin-1 ß (prolL-1 ß) in human macrophages and keratinocytes, and its downregulation results in reduced secretion of IL-1 ß. IL-1ß activation and secretion requires the proteolytic cleavage of prolL-1ß by caspase-1, which in turn is actìvated by a protein complex called the inflammasome. As it has been demonstrated that EBBP can bind two different proteins of the inflammasome (NALP-1 and caspase 1), we assumed that EBBP plays a role in the regulation of inflammation and that the inflammasome, which has as yet only been described in ínflammatory cells, may also exist in keratinocytes. Indeed, I could show in my thesis that the inflammasome components are expressed in human keratinócytes at the RNA and protein level and also in vivo in human epidermis. After irradiation with a physiological dose of UVB, keratinocytes activated prolL-1ß and secreted prolL-1 a, IL-1 ß, prolL-18 and inflammasome proteins, although all these proteins lack a classical signal peptide. The secretion was dependent on caspase-1 activity, but not on de novo protein synthesis. Knock-down of NALP1 and -3, caspase-1 and -5, EBBP and Asc strongly reduced the secretion of IL-1 ß, demonstrating that also in keratinocytes inflammasome proteins are directly involved in maturation of this cytokine. These results demonstrate for the first time the presence of an active inflammasome in non-professional immune cells. Moreover, they show that UV irradiation is a stimulus for inflammasome activation in keratinocytes. For the analysis of the ín vivo functions of EBBP, transgenic mice overexpressing EBBP in the epidermis were generated. To examine the influence of EBBP overexpression on inflammatory processes, we subjected the mice to different challenges, which induce inflammation. Wound-healing, UVB irradiation and delayed hypersensitivity were tested, but we did not observe any phenotype in the K14-EBBP mice. Besides, a conditional ebbp knockout mouse has been obtained, which will allow to determine the effects of EBBP gene deletion in different tissues and organs. RESUME: EBBP est un membre encore mal connu de la famille des RBCC/TRIM (RING finger B-box coiled-coil/tripartite motif). Il est exprimé de manière ubiquitaire, et en particulier dans les kératinocytes. EBBP étant capable d'interagir avec la prointerleukine-1 ß (prolL-1 ß) dans les macrophages et les kératinocytes humains et de réguler la sécrétion de l'IL-1 ß, il est très probable que cette protéine est impliquée dans l'inflammation. L'activation et la sécrétion de l'IL-1 ß requièrent le clivage protéolytique de son précurseur prolL-1ß par la caspase-1, qui est elle-même activée par un complexe protéique appelé l'inflammasome. Comme il a été démontré qu'EBBP peut lier deux protéines de l'inflammasome (NALP-1 et caspase-1), nous avons émis l'hypothèse qu'EBBP joue un rôle dans la régulation de l'inflammation et que l'inflammasome, jusqu'ici décrit exclusivement dans des cellules inflammatoires, existe dans les kératinocytes. En effet, j'ai pu montrer dans ma thèse que les composants de l'inflammasome sont exprimés dans les kératinocytes humains ainsi que in vivo dans l'épiderme humain. Après irradiation avec une dose, physiologique d'UVB, les kératinocytes activent la prolL-1 ß et sécrètent la prolL-1a, l'IL-1 ß, la prolL-18 et des protéines de l'inflammasome, bien que toutes ces protéines soient dépourvues de peptide signal. La sécrétion dépend de la caspase-1 mais pas de la synthèse protéique de novo. Le knock-down de NALP-1 et -3, des caspase-1 et -5, d'EBBP et d'Asc réduit de manière marquée la sécrétion d'IL-1 ß, démontrant que dans les kératinocytes également, les protéines de l'inflammasome sont impliquées directement dans la maturation de cette cytokine. Ces résultats démontrent pour la première fois la présence d'un inflammasome actif dans des cellules immunitaires non professionnelles. De plus, ils montrent que l'irradiation aux UV est un stimulus pour l'activation de l'inflammasome dans les kératinocytes. Pour l'analyse des fonctions d'EBBP in vivo, nous avons généré des souris transgéniques qui surexpriment EBBP dans l'épiderme. En vue d'examiner l'influence de la surexpression d'EBBP sur le processus inflammatoire, nous avons soumis ces souris à differents modèles d'inflammation. Nous avons testé cicatrisation, UVB et hypersensibilité retardée, mais n'avons pas observé de phénotype chez les souris transgéniques. En parallèle, nous avons également généré des souris knock-out pour ebbp qui devraient nous permettre de déterminer les effets de la suppression d'EBBP dans différents tissus et organes.

Estimation of dynamic latent variable models using simulated nonparametric moments

Abstract. Given a model that can be simulated, conditional moments at a trial parameter value can be calculated with high accuracy by applying kernel smoothing methods to a long simulation. With such conditional moments in hand, standard method of moments techniques can be used to estimate the parameter. Because conditional moments are calculated using kernel smoothing rather than simple averaging, it is not necessary that the model be simulable subject to the conditioning information that is used to define the moment conditions. For this reason, the proposed estimator is applicable to general dynamic latent variable models. It is shown that as the number of simulations diverges, the estimator is consistent and a higher-order expansion reveals the stochastic difference between the infeasible GMM estimator based on the same moment conditions and the simulated version. In particular, we show how to adjust standard errors to account for the simulations. Monte Carlo results show how the estimator may be applied to a range of dynamic latent variable (DLV) models, and that it performs well in comparison to several other estimators that have been proposed for DLV models.

Les symbioses agro-industrielles en Afrique de l'Ouest : évaluation du potentiel d'une nouvelle stratégie pour un développement durable

RésuméCette thèse traite de l'utilisation des concepts de Symbiose Industrielle dans les pays en développement et étudie le potentiel de cette stratégie pour stimuler un développement régional durable dans les zones rurales d'Afrique de l'Ouest. En particulier, lorsqu'une Symbiose Industrielle est instaurée entre une usine et sa population alentour, des outils d'évaluation sont nécessaires pour garantir que le projet permette d'atteindre un réel développement durable. Les outils existants, développés dans les pays industrialisés, ne sont cependant pas complètement adaptés pour l'évaluation de projets dans les pays en développement. En effet, les outils sont porteurs d'hypothèses implicites propres au contexte socio-économique dans lequel ils ont été conçus.L'objectif de cette thèse est de développer un cadre méthodologique pour l'évaluation de la durabilité de projets de Symbiose Industrielle dans les pays en développement.Pour ce faire, je m'appuie sur une étude de cas de la mise en place d'une Symbiose Industrielle au nord du Nigéria, à laquelle j'ai participé en tant qu'observatrice dès 2007. AshakaCem, une usine productrice de ciment du groupe Lafarge, doit faire face à de nombreuses tensions avec la population rurale alentour. L'entreprise a donc décidé d'adopter une nouvelle méthode inspirée des concepts de Symbiose Industrielle. Le projet consiste à remplacer jusqu'à 10% du carburant fossile utilisé pour la cuisson de la matière crue (calcaire et additifs) par de la biomasse produite par les paysans locaux. Pour ne pas compromettre la fragile sécurité alimentaire régionale, des techniques de lutte contre l'érosion et de fertilisation naturelle des sols sont enseignées aux paysans, qui peuvent ainsi utiliser la culture de biomasse pour améliorer leurs cultures vivrières. A travers cette Symbiose Industrielle, l'entreprise poursuit des objectifs sociaux (poser les bases nécessaires à un développement régional), mais également environnementaux (réduire ses émissions de CO2 globales) et économiques (réduire ses coûts énergétiques). Elle s'ancre ainsi dans une perspective de développement durable qui est conditionnelle à la réalisation du projet.A travers l'observation de cette Symbiose et par la connaissance des outils existants je constate qu'une évaluation de la durabilité de projets dans les pays en développement nécessite l'utilisation de critères d'évaluation propres à chaque projet. En effet, dans ce contexte, l'emploi de critères génériques apporte une évaluation trop éloignée des besoins et de la réalité locale. C'est pourquoi, en m'inspirant des outils internationalement reconnus comme l'Analyse du Cycle de Vie ou la Global Reporting Initiative, je définis dans cette thèse un cadre méthodologique qui peut, lui, être identique pour tous les projets. Cette stratégie suit six étapes, qui se réalisent de manière itérative pour permettre une auto¬amélioration de la méthodologie d'évaluation et du projet lui-même. Au cours de ces étapes, les besoins et objectifs en termes sociaux, économiques et environnementaux des différents acteurs sont déterminés, puis regroupés, hiérarchisés et formulés sous forme de critères à évaluer. Des indicateurs quantitatifs ou qualitatifs sont ensuite définis pour chacun de ces critères. Une des spécificités de cette stratégie est de définir une échelle d'évaluation en cinq graduations, identique pour chaque indicateur, témoignant d'un objectif totalement atteint (++) ou pas du tout atteint (--).L'application de ce cadre méthodologique à la Symbiose nigériane a permis de déterminer quatre critères économiques, quatre critères socio-économiques et six critères environnementaux à évaluer. Pour les caractériser, 22 indicateurs ont été définis. L'évaluation de ces indicateurs a permis de montrer que le projet élaboré atteint les objectifs de durabilité fixés pour la majorité des critères. Quatre indicateurs ont un résultat neutre (0), et un cinquième montre qu'un critère n'est pas atteint (--). Ces résultats s'expliquent par le fait que le projet n'en est encore qu'à sa phase pilote et n'a donc pas encore atteint la taille et la diffusion optimales. Un suivi sur plusieurs années permettra de garantir que ces manques seront comblés.Le cadre méthodologique que j'ai développé dans cette thèse est un outil d'évaluation participatif qui pourra être utilisé dans un contexte plus large que celui des pays en développement. Son caractère générique en fait un très bon outil pour la définition de critères et indicateurs de suivi de projet en terme de développement durable.SummaryThis thesis examines the use of industrial symbiosis in developing countries and studies its potential to stimulate sustainable regional development in rural areas across Western Africa. In particular, when industrial symbiosis is instituted between a factory and the surrounding population, evaluation tools are required to ensure the project achieves truly sustainable development. Existing tools developed in industrialized countries are not entirely suited to assessing projects in developing countries. Indeed, the implicit hypotheses behind such tools reflect the socioeconomic context in which they were designed. The goal of this thesis is to develop a methodological framework for evaluating the sustainability of industrial symbiosis projects in developing countries.To accomplish this, I followed a case study about the implementation of industrial symbiosis in northern Nigeria by participating as an observer since 2007. AshakaCem, a cement works of Lafarge group, must confront many issues associated with violence committed by the local rural population. Thus, the company decided to adopt a new approach inspired by the concepts of industrial symbiosis.The project involves replacing up to 10% of the fossil fuel used to heat limestone with biomass produced by local farmers. To avoid jeopardizing the fragile security of regional food supplies, farmers are taught ways to combat erosion and naturally fertilize the soil. They can then use biomass cultivation to improve their subsistence crops. Through this industrial symbiosis, AshakaCem follows social objectives (to lay the necessary foundations for regional development), but also environmental ones (to reduce its overall CO2 emissions) and economical ones (to reduce its energy costs). The company is firmly rooted in a view of sustainable development that is conditional upon the project's execution.By observing this symbiosis and by being familiar with existing tools, I note that assessing the sustainability of projects in developing countries requires using evaluation criteria that are specific to each project. Indeed, using generic criteria results in an assessment that is too far removed from what is needed and from the local reality. Thus, by drawing inspiration from such internationally known tools as Life Cycle Analysis and the Global Reporting Initiative, I define a generic methodological framework for the participative establishment of an evaluation methodology specific to each project.The strategy follows six phases that are fulfilled iteratively so as to improve the evaluation methodology and the project itself as it moves forward. During these phases, the social, economic, and environmental needs and objectives of the stakeholders are identified, grouped, ranked, and expressed as criteria for evaluation. Quantitative or qualitative indicators are then defined for each of these criteria. One of the characteristics of this strategy is to define a five-point evaluation scale, the same for each indicator, to reflect a goal that was completely reached (++) or not reached at all (--).Applying the methodological framework to the Nigerian symbiosis yielded four economic criteria, four socioeconomic criteria, and six environmental criteria to assess. A total of 22 indicators were defined to characterize the criteria. Evaluating these indicators made it possible to show that the project meets the sustainability goals set for the majority of criteria. Four indicators had a neutral result (0); a fifth showed that one criterion had not been met (--). These results can be explained by the fact that the project is still only in its pilot phase and, therefore, still has not reached its optimum size and scope. Following up over several years will make it possible to ensure these gaps will be filled.The methodological framework presented in this thesis is a highly effective tool that can be used in a broader context than developing countries. Its generic nature makes it a very good tool for defining criteria and follow-up indicators for sustainable development.

The role of Pten in the Hematopoietic System and the Hematopoietic Stem Cells

Résumé Identification, localisation et activation des cellules souches hématopoiétiques dormantes in vivo Les cellules souches somatiques sont présentes dans la majorité des tissus régénératifs comme la peau, l'épithélium intestinal et le système hématopoiétique. A partir d'une seule cellule, elles ont les capacités de produire d'autres cellules souches du même type (auto-renouvellement) et d'engendrer un ensemble défini de cellules progénitrices différenciées qui vont maintenir ou réparer leur tissu hôte. Les cellules souches adultes les mieux caractérisées sont les cellules souches hématopoiétiques (HSC), localisées dans la moelle osseuse. Un des buts de mon travail de doctorat était de caractériser plus en profondeur la localisation des HSCs endogènes in vivo. Pour ce faire, la technique "label retaining assay", se basant sur la division peu fréquentes et sur la dormance des cellules souches, a été utilisée. Après un marquage des souris avec du BrdU (analogue à l'ADN) suivi d'une longue période sans BrdU, les cellules ayant incorporés le marquage ("label retaining cells" LCRs) ont pu être identifiées dans la moelle osseuse. Ces cellules LCRs étaient enrichies 300 fois en cellules de phenotype HSC et, en utilisant de la cytofluorométrie, il a pu être montré qu'environ 15% de toutes les HSCs d'une souris restent dormantes durant plusieures semaines. Ces HSCs dormantes à long terme ne sont probablement pas impliquées dans la maintenance de 'hématopoièse. Par contre, on assiste à l'activation rapide de ces HSCs dormantes lors d'une blessure, comme une ablation myéloide. Elles re-entrent alors en cycle cellulaire et sont essentielles pour une génération rapide des cellules progénitrices et matures qui vont remplacer les cellules perdues. De plus, la détection des LCRs, combinée avec l'utilisation du marqueur de HSCs c-kit, peut être utilisée pour la localisation des HSCs dormantes présentes dans la paroi endostéale de la cavité osseuse. De manière surprenante, les LCRs c-kit+ ont surtout étés trouvées isolées en cellule unique, suggérant que le micro-environement spécifique entourant et maintenant les HSCs, appelé niche, pourrait être très réduit et abriter une seule HSC par niche. Rôles complexes du gène supresseur de tumeur Pten dans le système hématopoiétique La phosphatase PTEN disparaît dans certains cancers héréditaires ou sporadiques humains, comme les gliomes, les cancers de l'utérus ou du sein. Pten inhibe la voie de signalisation de la PI3-kinase et joue un rôle clé dans l'apoptose, la croissance, la prolifération et la migration cellulaire. Notre but était d'étudier le rôle de Pten dans les HSC normale et durant la formation de leucémies. Pour ce faire, nous avons généré un modèle murin dans lequel le gène Pten peut être supprimé dans les cellules hématopoiétiques, incluant les HSCs. Ceci a été possible en croissant l'allèle conditionnelle ptenflox soit avec le transgène MxCre inductible par l'interféron α soit avec le transgène Scl-CreERt inductible par le tamoxifen. Ceci permet la conversion de l'allèle ptenflox en l'allèle nul PtenΔ dans les HSCs et les autres types cellulaires hématopoiétiques. Les souris mutantes Pten développent une splénomégalie massive causée par une expansion dramatiques de toutes les cellules myéloides. De manière interessante, alors que le nombre de HSCs dans la moelle osseuse diminue progressivement, le nombre des HSCs dans la rate augmente de manière proportionnelle. Etrangement, les analyses de cycle cellulaire ont montrés que Pten n'avait que peu ou pas d'effet sur la dormance des HSCs ou sur leur autorenouvellement. En revanche, une augmentation massive du niveau de la cytokine de mobilisation G-CSF a été détéctée dans le serum sanguin, suggérant que la suppression de Pten stimulerait la mobilisation et la migration des HSC de la moelle osseuse vers la rate. Finallement, la transplantation de moelle osseuse délétée en Pten dans des souris immuno-déficientes montre que Pten fonctionnerait comme un suppresseur de tumeur dans le système hématopoiétique car son absence entraîne la formation rapide de leucémies lymphocytaires. Summary Identification, localization and activation of dormant hematopoietic stun cells in vivo Somatic stem cells are present in most self-renewing tissues including the skin, the intestinal epithelium and the hematopoietic system. On a single cell basis they have the capacity to produce more stem cells of the same phenotype (self-renewal) and to give rise to a defined set of mature differentiated progeny, responsible for the maintenance or repair of the host tissue. The best characterized adult stem cell is the hematopoietic stem cell (HSC) located in the bone marrow. One goal of my thesis work was to further characterize the location of endogenous HSCs in vivo. To do this, a technique called "label retaining assay» was used which takes advantage of the fact that stem cells (including HSCs) divide very infrequently and can be dormant for months. After labeling mice with the DNA analogue BrdU followed by a long BrdU free "chase", BrdU "label retaining cells" (CRCs) could be identified in the bone marrow. These CRCs were 300-fold enriched for phenotypic HSCs and by using flow cytometry analysis it could be shown that about 15% of all HSCs in the mouse are dormant for many weeks. Our results suggest that these long-term dormant HSCs are unlikely to be involved in homeostatic maintenance. However they are rapidly activated and reenter the cell cycle in response to injury signals such as myeloid ablation. In addition, detection of LRCs in combination with the HSC marker c-Kit could be used to locate engrafted dormant HSCs close to the endosteal lining of the bone marrow cavities. Most surprisingly, c-Kit+LRCs were found predominantly as single cells suggesting that the specific stem cell maintaining microenvironment, called niche, has limited space and may house only single HSCs. Complex roles of the tumor suppressor gene Pten in the hematopoietic system. The phosphatase PTEN is lost in hereditary and sporadic forms of human cancers, including gliomas, endometrial and breast cancers. Pten inhibits the PI3-kina.se pathway and plays a key role in apoptosis, cell growth, proliferation and migration. Our aim was to study the role of Pten in normal HSCs and during leukemia formation. To do this, we generated a mouse model in which the Pten gene can be deleted in hematopoietic cells including HSCs. This was achieved by crossing the conditional ptenflox allele with either the interferona inducible MxCre or the tamoxifen inducible Scl-CreERT transgene. This allowed the conversion of the ptenflox allele into a pterr' null allele in HSCs and other hematopoietic cell types. As a result Pten mutant mice developed massive splenomegaly due to a dramatic expansion of all myeloid cells. Interestingly, while the number of bone marrow HSCs progressively decreased, the number of HSCs in the spleen increased to a similar extent. Unexpectedly, extensive cell cycle analysis showed that Pten had little or no effect on HSC dormancy or HSC self-renewal. Instead, dramatically increased levels of the mobilizing cytokine G-CSF were detected in the blood serum suggesting that loss-of Pten stimulates mobilization and migration of HSC from the BM to the spleen. Finally, transplantation of Pten deficient BM cells into immuno-compromised mice showed that Pten can function as a tumor suppressor in the hematopoietic system and that its absence leads to the rapid formation of T cell leukemia.

IL-13 induces expression of CD36 in human monocytes through PPARgamma activation.

The class B scavenger receptor CD36 is a component of the pattern recognition receptors on monocytes that recognizes a variety of molecules. CD36 expression in monocytes depends on exposure to soluble mediators. We demonstrate here that CD36 expression is induced in human monocytes following exposure to IL-13, a Th2 cytokine, via the peroxisome proliferator-activated receptor (PPAR)gamma pathway. Induction of CD36 protein was paralleled by an increase in CD36 mRNA. The PPARgamma pathway was demonstrated using transfection of a PPARgamma expression plasmid into the murine macrophage cell line RAW264.7, expressing very low levels of PPARgamma, and in peritoneal macrophages from PPARgamma-conditional null mice. We also show that CD36 induction by IL-13 via PPARgamma is dependent on phospholipase A2 activation and that IL-13 induces the production of endogenous 15-deoxy-Delta12,14-prostaglandin J2, an endogenous PPARgamma ligand, and its nuclear localization in human monocytes. Finally, we demonstrate that CD36 and PPARgamma are involved in IL-13-mediated phagocytosis of Plasmodium falciparum-parasitized erythrocytes. These results reveal a novel role for PPARgamma in the alternative activation of monocytes by IL-13, suggesting that endogenous PPARgamma ligands, produced by phospholipase A2 activation, could contribute to the biochemical and cellular functions of CD36.

Regulation of adaptive behaviour during fasting by hypothalamic Foxa2.

The lateral hypothalamic area is considered the classic 'feeding centre', regulating food intake, arousal and motivated behaviour through the actions of orexin and melanin-concentrating hormone (MCH). These neuropeptides are inhibited in response to feeding-related signals and are released during fasting. However, the molecular mechanisms that regulate and integrate these signals remain poorly understood. Here we show that the forkhead box transcription factor Foxa2, a downstream target of insulin signalling, regulates the expression of orexin and MCH. During fasting, Foxa2 binds to MCH and orexin promoters and stimulates their expression. In fed and in hyperinsulinemic obese mice, insulin signalling leads to nuclear exclusion of Foxa2 and reduced expression of MCH and orexin. Constitutive activation of Foxa2 in the brain (Nes-Cre/+;Foxa2T156A(flox/flox) genotype) results in increased neuronal MCH and orexin expression and increased food consumption, metabolism and insulin sensitivity. Spontaneous physical activity of these animals in the fed state is significantly increased and is similar to that in fasted mice. Conditional activation of Foxa2 through the T156A mutation expression in the brain of obese mice also resulted in improved glucose homeostasis, decreased fat and increased lean body mass. Our results demonstrate that Foxa2 can act as a metabolic sensor in neurons of the lateral hypothalamic area to integrate metabolic signals, adaptive behaviour and physiological responses.